200 amp alternator- No output, questions.

Hi all,

I have a very early USMC M998 with 3-speed transmission. In 2005, it was refitted with a 6.5L engine with the 200 amp alternator.

When I start the truck, the alternator no longer puts out any power and the smart-start box keeps cycling the glow plugs.
The problem seems intermittent. I was troubleshooting when suddenly, the problem resolved itself the first time.
As of yesterday, the problem is being persistent, and the alternator will not "start."

Question #1: Is the smart-start box continually hitting the glow plugs because it's missing a voltage signal from the alternator?
Or do I have it backwards, that the smart-start box is not sending an energize signal to the alternator?

Question #2: Can a competent auto electrical shop rebuild this unit or are parts not readily available?

Question #3: Would refitting early style 60 amp alternator be a less expensive, more DIY repair friendly option?
Can I use the existing wire harness?
What bracket do I need?

Sounds like the start box is failing and needs repaired/replaced.
The alternator has zero control over the glow plug operation
Alternator won't start until it gets a signal from the start box
60 amp alternator is considered a major downgrade. If you are going to do anything, it would probably be more reliable to change to an aftermarket/civilian type 24V alternator

@Coug Ah, ok. I knew there was a relationship of some sort between the two.
I downloaded the 200a alternator troubleshooting guide. The steps are simple enough.

For testing purposes, is there a way to simulate the signal from the start box to trick the alternator into starting?

Ajax MD said:

@Coug Ah, ok. I knew there was a relationship of some sort between the two.
I downloaded the 200a alternator troubleshooting guide. The steps are simple enough.

For testing purposes, is there a way to simulate the signal from the start box to trick the alternator into starting?

Click to expand...

You need to troubleshoot the problem, the first question I would ask is if the heater motor is working?
The heater gets its power from the same relay that excites the alternator.
In any case you also need to check and make sure you have 24V going to the IGN terminal on the regulator.
It does sound like a possible EESS box failure.
Here is the troubleshooting guide for the alt.

Ajax MD said:

@Coug Ah, ok. I knew there was a relationship of some sort between the two.
I downloaded the 200a alternator troubleshooting guide. The steps are simple enough.

For testing purposes, is there a way to simulate the signal from the start box to trick the alternator into starting?

Click to expand...

As Mogman said, checking for voltage at the ign terminal should tell you whether it's getting the signal to produce power or not. If it is and still not producing power, then I'd worry about further troubleshooting of the alt.
Because it's intermittent, then it's 98% likely it's a failed regulator IF it's getting the proper voltage on the IGN terminal.
But multiple systems that all tie into the start box points towards a start box issue, so at minimum you should probably troubleshoot it before pulling out your hair trying to troubleshoot the alternator.

It’s not a signal at the IGN terminal, it’s 24v that is from turning on the ignition to “run”, that comes through the “EESS” box.
No 24v? the generator doesn’t know the generator is turning, once it’s turning, it waits to see a stable speed of rotation, this is part of the
soft start feature.

Mogman said:

You need to troubleshoot the problem, the first question I would ask is if the heater motor is working?
The heater gets its power from the same relay that excites the alternator.
In any case you also need to check and make sure you have 24V going to the IGN terminal on the regulator.
It does sound like a possible EESS box failure.
Here is the troubleshooting guide for the alt.

Click to expand...

Hi Mog, yes, the blower motor still works. I've downloaded that troubleshooting guide and I'll report back after I've run through it.

Coug said:

As Mogman said, checking for voltage at the ign terminal should tell you whether it's getting the signal to produce power or not. If it is and still not producing power, then I'd worry about further troubleshooting of the alt.
Because it's intermittent, then it's 98% likely it's a failed regulator IF it's getting the proper voltage on the IGN terminal.
But multiple systems that all tie into the start box points towards a start box issue, so at minimum you should probably troubleshoot it before pulling out your hair trying to troubleshoot the alternator.

Click to expand...

It's only self-corrected once. Sort of intermittent.

You guys have put me on the path. I'll walk it awhile and let you know where it takes me.

Grrr... I went to test everything out and the alternator is working.
I'm pretty certain that it's the EESS box now. Obviously, I'll confirm this with the test procedure when it fails again.

I have the Presolite box, not Nartron. Black, silver label.
My understanding is that Thou Shalt Not Mix Prestolite/Nartron/KDS boxes with later model Nartron/KDS temperature control units.
Can Presolite boxes even be found anymore? Can they be rebuilt?

That junk Prestolite box only works with GPC 12338772.
It should be replaced......and your glow plugs are soon to be or already toast.

Ajax MD said:

Grrr... I went to test everything out and the alternator is working.
I'm pretty certain that it's the EESS box now. Obviously, I'll confirm this with the test procedure when it fails again.

I have the Presolite box, not Nartron. Black, silver label.
My understanding is that Thou Shalt Not Mix Prestolite/Nartron/KDS boxes with later model Nartron/KDS temperature control units.
Can Presolite boxes even be found anymore? Can they be rebuilt?

Click to expand...

that box you have is a PCB, it’s got it own dedicated glow plug controller in the water crossover, not a TSU….TSU is only used in EESS series boxes. You are on borrowed time with that old PCB.

Retiredwarhorses said:

that box you have is a PCB, it’s got it own dedicated glow plug controller in the water crossover, not a TSU….TSU is only used in EESS series boxes. You are on borrowed time with that old PCB.

Click to expand...

Ah, ok. So either find another Prestolite box or do a multi-point upgrade to some sort of EESS and a TSU and probably glow plugs as well.

I've had this truck for...3-4 years now. It starts like a champ in very cold weather so I don't think the glow plugs are fried, yet.

Read the link posted in my signature line for options on potentially repairing and improving the PCB.